This invention relates to an elastomeric bearing and in particular, although not exclusively, to a heavy duty part-spherical type bearing for accommodating relative conical movement between two components.
In the construction of underwater oil well pipelines connecting to a floating structure it is often necessary to incorporate heavy duty elastomeric bearings to accommodate the effect of movement of a floating platform relative to the sea bed without undue strain on interconnecting pipework.
A similar requirement for heavy duty elastomeric bearings arises also in relation to tether lines for mooring floating platform structure.
In one known form of elastomeric bearing an annular element of elastomeric material is provided between confronting annular faces of a pair of rigid members; typically those faces are inclined to both the longitudinal axis of the bearing and a plane perpendicular thereto and commonly are of a part-spherical shape. To ensure an ability for the elastomeric material to withstand high compressive loads it is known that reinforcing metal interleaves may be provided in the elastomeric material, typically to lie in planes substantially parallel with the aforementioned inclined faces of the rigid members. Said reinforcing interleaves serve to transmit forces between successive elastomeric layers and do not directly transmit forces to or from structure external of the bearing.
In this construction the metal interleaves prevent over-stressing of the elastomeric material interleaves interposed therebetween but themselves become subject to high stress by virtue of variations of the hydrostatic pressure in the elastomeric layers between which a metal interleaf is interposed. Especially if the bearing is required to accommodate a large degree of conical movement and/or is subject to a large number of cycles of conical movement there is a risk of failure of the metal interleaf.
The potential problem of failure of a metal layer interleaf is not confined to elastomeric bearings comprising an annular element of elastomeric material. Thus, in chevron type springs comprising a pair of rigid end members of V-shape in section and having sandwiched therebetween a layer of elastomeric material of V-shape in form, it is known to provide within the elastomeric material interleaving reinforcing metal layers each in the form of metal plates bent to a V-shape. It is found that fatigue failure of those plates also can arise.